| Summary: | 碩士 === 國立中興大學 === 農藝學系所 === 102 === Fluazifop-P-butyl, a selective graminicide, is widely used to control annual grass weeds. The action mechanism of this herbicide is to inhibit the activity of acetyl-CoA carboxylase (ACCase; EC 6.4.1.2), which is responsible for the lipid biosynthesis. In order to explore the resistance mechanism, resistant (R)- and susceptible (S)-biotype of goosegrass [Eleusine indica (L.) Gaertn.] treated with 14C-fluazifop-P-butyl were studied. Although no significant difference of herbicide uptake between R- and S-biotype, and even the higher translocation rate of 14C-fluazifop and its metabolites in R-biotype was found, it is suggested that the herbicide metabolism is involved in resistance mechanism due to the more polar metabolites were found in R-biotype.
According to the results of mass spectrum analysis, six signals including m/z 512, 432, 423, 415, 314 and 160 under POS scanning mode, and four signals including m/z 788, 623, 593 and 162 under NEG scanning mode appeared in both R- and S-biotype. These signals had stronger intensities in R-biotype, except m/z 162. Interestingly, six signals including m/z 202.180, 219.012, 255.944, 288.963, 310.156 and 340.865, only appeared in R-biotype, and twenty-one signals including m/z 333.011, 525.977, 631.027, 647.003, 688.030, 827.067, 941.060, 989.120, 182.034, 191.039, 200.044, 214.918, 265.023, 322.937, 328.887, 338.343, 352.948, 365.107, 374.038, 381.080 and 394.920 only appeared in S-biotype, suggesting different metabolite profile between R- and S-biotype. In this metabolite study, the generation of 2-[4-(5-trifluoro- methyl-2-pyridyloxy)phenoxy] propanol, 5-trifluoromethyl-2-hydroxy- pyridine and 5-trifluoromethyl-2-pyridine suggested that certain reduction reaction might be happened. Therefore, we attempted to clarify the role of cytochrome P450 reductase (CYP; EC 1.2.6.4) in fluazifop metabolism.
Coupled with the study on the activity of cytochrome P450 reductase, it is suggests that fluazifop-P-butyl in goosegrass was hydrolyzed to fluazifop acid, and then reduced to 2-[4-(5-trifluoromethyl-2-pyridyloxy) phenoxy] propanol by cytochrome P450 reductase. Subsequently, 4-(5-trifluoromethyl-2-puridyl)oxyphenol was formed, and both 5-tri- fluoromethyl-2-hydroxy-pyridine and 5-trifluoromethyl-2-pyridone were formed through reduction catalyzed by cytochrome P450 reductase.
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